A synthetic fiber or a resin composed of polyurethane, polyether, polyester, polyamide, polyethylene, polypropylene, polystyrene, polyacetal or the like, which comprises a polymer alone, is known to suffer oxidative degradation, such as aging, changing in color or loss in desirable mechanical properties by heat during the processing step or light during their service.
In order to solve the above problems, the following methods are proposed.
(1) It has been well known that various kinds of phenol-type antioxidants are added to a synthetic fiber or a synthetic resin during the production or processing process. For example, 2,6-di-t-butyl-4-methylphenol, 4,4'-butylidenebis(3-methyl-6-t-butylphenol), tetrakis[methylene-3-(3', 5'- di-t-butyl-4'-hydroxyphenyl)propionate]methane,1,3,5-trimethyl- 2,4,6-tris(3,5-di-t-butyl-4-hydroxybenzyl)benzene, tris(3,5-di-t-butyl-4-hydroxybenzyl)isocyanurate, tris(2,6-dimethyl-4-t-butyl-3-hydroxybenzyl)isocyanurate and the like can be used.
(2) Further, it has been recently proposed to use an antioxidant having high-molecular weight. For example, a polyurethane elastic fiber containing a polyaddition compound of p-cresol and divinylbenzene (Japanese Patent Publication No. 6510/1972), a phenol acrylate ester polymer (Japanese Patent Publication No. 34667/1974), an isopropenyl phenol olygomer (Japanese Patent Laid Open Publication No. 20247/1976), an antioxidant containing o-substituted phenol novolak as a main ingredient (Japanese Laid Open Publication No. 71912/1983).
According to the above conventional method (1), however, an antioxidant is scattered during a processing step, or a product is discolored during its service life. Especially, it has insufficient properties to be used for a synthetic fiber.
As for the above conventional method (2), it is effective, to some extent, to prevent scattering of an antioxidant or to improve its resistance upon usage such as its dry-cleaning resistance in a fabric in comparison with usage of an antioxidant having low-molecular weight. This method, however, inadvantageously involves complicated processes in purification of a starting material or producing. Further, such antioxidant itself is remarkably colored, therefore its applications are restricted.
In order to solve the above mentioned problems, the present inventors have intensively studied. As the result, there has been found a polymeric antioxidant with excellent properties and the production thereof, which can be obtained by using a commercially available starting material without any purification.